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Halligan Water Supply Project

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Minimizing Impacts

Minimizing Impacts

Dry river bed next to a pool on North Fork of the Poudre River at Cherokee Park Road


While all water supply projects have impacts, the best projects include environmental benefits that outweigh the impacts. Our focus on stewardship has guided decisions related to the Halligan Water Supply Project and has gained the project recognition as an “acceptable planned project” by Western Resource Advocates.

All environmental impacts associated with the project, positive and negative, are thoroughly evaluated through the federal permitting process. Impacts are further evaluated through the state and county permitting processes. Appropriate avoidance and mitigation of negative impacts will be required before permits are issued. The environmental impacts are disclosed in a draft Environmental Impact Statement (EIS).

The project will make every effort to minimize environmental impacts, primarily through enlargement of an existing reservoir and dam rather than constructing a new one.

Additionally, the City of Fort Collins has committed to improved reservoir operations that provide minimum flows to the North Fork of the Poudre River year-round. Currently, the river often runs dry at various times throughout the year, which stresses fish and other wildlife. The minimum flows planned after the reservoir expansion will reconnect habitat that is currently segmented downstream of the reservoir.

Mitigation process

Three-step mitigation process.


Most of the negative environmental impacts will occur along the existing Halligan shoreline and upstream of the reservoir along a ¾-mile stretch of the North Fork of the Poudre River. These areas will be newly inundated from the reservoir expansion. Other negative impacts will be temporary and related to construction. Each impact has been thoroughly evaluated and are described in the draft EIS

The City of Fort Collins is developing concepts to mitigate impacts from enlarging Halligan Reservoir, as well as enhance the current conditions in the area around the reservoir. The City present these conceptual plans in a Conceptual Mitigation Plan that is available for public review wtih the draft EIS (released by the U.S. Army Corps of Engineers).

The first step in mitigation is designing a project that avoids impacts. This is achieved for the Halligan Water Supply Project by using existing infrastructure and minimizing the area of the reservoir.

The next step in mitigation is minimizing impacts. For example, the Halligan Water Supply Project includes operational measures to increase flows downstream and improve habitat along the North Fork of the Poudre River.

The final step in mitigation is compensating for unavoidable impacts. An example of this is replacing lost habitat function in wetland and riparian areas in the same watershed.  

These mitigation measures are still conceptual in nature and subject to input from the public and reviewing agencies. Some example measures that will be included in the Conceptual Mitigation Plan are:

North Fork Habitat Improvement
The Halligan Water Supply Project is designed to:

  • Establish minimum flows in the North Fork year-round
  • Reconstruct the North Poudre Canal diversion to allow flow bypass
  • Include a peak flow bypass program to allow critical flushing flows
  • Include an environmental pool to augment low river flows until full reservoir capacity is needed

Inundated Wetlands and Riparian Resources 
Several options are being considered for mitigation of impacted wetlands and riparian resources, including restoration or enhancement of land along the North Fork or on Robert’s Ranch, where the City owns a conservation easement on approximately 400 acres.

Fish Habitat Improvement
Two potential options are being considered to enhance the existing fish habitat downstream of Halligan Reservoir:

  • A new North Poudre Canal diversion will allow fish bypass and increase connectivity.
  • The reintroduction of a pure-strain greenback cutthroat trout in a 6-mile stretch of the North Fork below Halligan Reservoir.

Cultural and Paleontological Resources
Surveys will be conducted prior to construction and plans will be developed to protect identified resources. If any paleontological resources are discovered during construction, contractors will be required to stop work until a survey can be conducted.

Wildlife and Special Status Species 
Impacts to wildlife and special status species will be mitigated by minimizing the project’s footprint and restoring or enhancing degraded habitat along the North Fork or on Roberts Ranch.

Water Quality
Design of the raised dam would include a multilevel outlet tower.

Air Quality
A plan will be developed to control dust and other air emissions during construction.

Other Construction Impacts

  • Revegetation
  • Restoration of disturbed areas and access roads
  • Traffic, stormwater and noxious weed control

Public Recreation
Fort Collins Utilities is considering opening a portion of Halligan Reservoir and the north shoreline to seasonal fishing access.

Downloadable Mitigation Map

Strong Stewardship Ethic

North Fork of the Poudre River at Cherokee Park Road

Main Stem of the Cache la Poudre River.


The City of Fort Collins has a strong stewardship ethic that provides the foundation for the management of current and future water use in the Poudre Basin.

Since 2008, Utilities Watershed Program has lead a collaborative upper Cache la Poudre Water Quality Monitoring Program that also includes the City of Greeley and Soldier Canyon Water Authority. This monitoring program assists partners in meeting current and future drinking water treatment goals by reporting seasonal, short-term and long-term trends using a series of source water quality monitoring reports.

In 2016, Utilities Watershed Program, with assistance from multiple other stakeholders, completed a Source Water Protection Plan (SWPP) for the upper Poudre River and Horsetooth Reservoir Watersheds. The SWPP identifies potential sources of contamination to water supplies; ranks those sources according to risk to the City’s drinking water infrastructure and source water quality; and identifies best management practices to mitigate those risks. Forest health/wildfires was identified as the highest priority threat.

Also in 2016, the Coalition for the Poudre River Watershed (CPRW), Fort Collins Utilities and other community stakeholders completed the Poudre River Watershed Resiliency Plan. The plan is used by the Watershed Program to prioritize watershed protection projects in the upper Poudre River Watershed. The Watershed Program continues to work collaboratively with CPRW and other partners on wildfire restoration and mitigation projects to improve the health and resiliency of the Poudre River Watershed.